Method for obtaining corrosion and tuberculation inhibition in water systems



Nov. 7, 1950 w. L. NIELAND n AL 2,529,178

METHOD FOR OBTAINING, CORROSION AND TUBERCULATION wlLuAm 1.. JOHN J.

CHARLES BY HARZY L. KAHLE t/ INHIBITION IN WATER SYSTEMS Filed Dec. 1947 I} no CONCENTRATION, PPM

0 M TARO o LIE om 0 s n M A Patented Nov. 7, 1950 METHOD FOR OBTAINING CORROSION AND TUBERCULATION INHIBITION IN WATER SYSTEMS William L. Nieland, Downers Grove, Ill., and John J. Maguire, Elkins Park, Charles B. Philadelphia, and Barry L. ville, Pa., assignors to W. Philadelphia, Pa., a flrm George, Kahler, Feaster- H. and L. D. Betz,

Application December 6, 1947, Serial No. 790.088

7 Claims.

Our invention relates to the protection of metals, particularly ferrous metals, from waterside corrosion in water systems.

The present methods in commercial use in municipal and industrial fields employ the alkalies, silicates and phosphates. The principal objects of our invention consist in providing an inhibitor which will afford better protection, employing lower concentrations and at lower cost than that secured by previous known materials. Additional objects are, to provide an inhibitor having the physical and chemical characteristics, in the effective concentration required, of being non-toxic; and capable of being advantageously used without materially affecting the hardness, the total ion content, or the pH of the water; which may be effectively employed regardless of the hardness of the water ordinarily encountered in water systems; and which would, in the oncethrough requirement of the continuously moving water be effective, in low concentrations to inhibit the further corrosion and tuberculation in existing systems.

Tuberculation in domestic and municipal systems reduces the effective inside diameter and carrying capacity of the pipe, resulting in excessive pressure losses and increased pumping costs. Eventually, a point is reached where costly cleaning must be attempted or the equipment replaced. Red water also results from the sloughing oil of this tuberculation. A further object is to provide a product havin the aforesaid characteristics which will remove existing tuberculation products.

We have shown in our concurrently filed application entitled Corrosion and Tuberculation In hibition in Water Systems made a part hereof, that the hydroxy polycarboxylates possess the aforementioned desirable properties in certain ranges of concentration. In the present application, we additionally disclose that other hydroxy carboxylates such as sodium gluconate exhibit similar characteristics.

Like the previously stated hydroxy polycarboxylates, sodium gluconate exhibits critical range of ellectiveness in inhibiting corrosion in lower concentrations, and below minimum and maximum values of concentrations, pitting of the metal takes plac which may result in perforation of the metal wall, despite a showing of a percent saving of metal. AbOVe certain minimum values, sodium gluconate too forms the protective coating which is hard, impervious, and tightly bonded to the metal, and which ceases to form after reaching a visible thickness. Thus additional objects of our invention are to determine (a) the exact conditions under which the protective layer can be established, (17) the practical minimum and maximum range of efiectiveness and (c) the critical pitting limitations.

We accomplish these and other objects as will be apparent from a consideration of the substances used, the methods of employing them, and the results obtained, as disclosed in the following specification, particularly pointed out in the attached claims and illustrated in the accompanying drawings in which:

Fig. 1 is a cross-sectional view of a metal waterpipe disclosing the character of the tuberculation and corrosion normally resulting from conducting untreated water therethrough.

Fig. 2 is a similar view of the pipe of Fig. 1 after continuous treatment by our method resulting in the formation of protective layer and the removal of the tuberculation products.

Fig. 3 is a cross-sectional view of a metal water pipe subjected, from its original installation, to continuous treatment by our method.

Fig. 4 is a chart indicating the results of a series of tests for various concentrations of sodium gluconate indicating the percent protection afforded.

In Figure l, we have illustrated a cross section of typical iron pipe I 0 wherein the original inside surface ll, indicated by dot-dash lines has been corroded and the thickness of the pipe reduced by the areas indicated by reference numeral I2. The original hollow portion of the pipe containing the water l3 has diminished in cross-sectional area by the tuberculation l4 until the water carrying surface I5 has been formed. As previously indicated, the reduction of the efiective inside diameter lowers the water carrying capacity of the pipe. I

In Fig. 2, the same pipe I0 is shown after treatment by our method. The treatment can be fed to the water system in any of the common commercial methods used for this purpose. A gravity drip feed can be used where applicable as can chemical pumps, by-pass feeders, eductors, or any type of solution feeder. The protective layer I 6 is formed under the porous tuberculation products, ultimately eliminating the tuberculation products and providing an increased water carrying capacity for the same pipe.

.In Figure 3, a section of new iron pipe I! is shown provided with a protective layer ill on the inner surface IS. The protective layer laid down on the metal underneath the water 20 by our method, has been found to eifectively inhibit corrosion and tuberculation. As a result, the carrying capacity of the pipe remains substantially at its original maximum, and the problems of corrosion and tuberculation are avoided.

In Fig. 4 we have charted the results of a series of tests using sodium gluconate for various concentrations indicating the percent protection afforded each concentration. Percent protection as used in Fig. 4 is equal to:

100 Xweight loss of control minus weight loss with inhibitor weight loss of control .By weight loss of control is meant the weight loss sustained by the corrosive specimen when no treatment is employed. In these tests, under the conditions of continuous flow, using Philadelphia tap water at 3.5 feet per second, at 120 F., containing 5.5 P. P.'M. dissolved oxygen and employing ferrous specimens, it is evident that there exists a zone of economical Protection between from about .1 P. P. M. to about 100 P. P. M. Below the minimum, no protection was afforded and above about 100 P. P. M., noadditional protection was secured for increased concentrations. ther investigations indicated that the ferrous metal specimens subjected to concentrations in the beneficial zone exhibited a dense dark coating which has a visible thickness. The coating is an iron compound, smooth, resistant to penetration by liquids, and so firmly bonded to the metal that its removal by physical and chemical means is exceedingly difificult. The inhibitor readily penetrates the porous tuberculation on corroded metal formed in the absence of hydroxy carboxylates and builds up a protective layer underneath and on the metal surface, which prevents further corrosion and tuberculation. With continuous treatment, the original products are gradually removed and passage of water made easier. The protective layer is not formed below .1 P. P. M. and protection against corrosion did not exist without the protective layer. The maximum degree of protection as measured by the percent metal saving was obtained in the vicinity of 100 P. P. M. It was also found that above about 100 P. P. M., the increase in concentration was accompanied by a pitting of the metal which, over a period of time, would cause a perforation in the metal wall of the specimen. While a degree of pitting occurs below 100 P. P. M., such pitting does not have the severity which occurs in concentrations above 100 P. P. M. Thus, the apparently unlimited upper beneficial range is limited actually to about 100 P. P. M. for the average of the hydroxy carboxylates. The practical range, therefore, operates from about .1 P. P. M. to about 100 P. P. M., the cost thereafter rising as the benefits decreased. It is also evident from the results that practical protection is neither a linear nor a continuous function of the concentration. It was apparent that gluconic acid and its soluble metal salts possess corrosive inhibiting and tuberculation removing properties similar to the hydroxy polycarboxylates such as citric, tartaric,

malic and mucic acids, particularly covered in our concurrently filed case, and that the conduct of all the hydroxy carboxylates in water has a substantial similarity. The protective layer formed exhibits similar characteristics and the effectiveness is substantially in the same general range.

Although we have used steel in the particular experiments illustrated in proving that hydroxy carboxylic acids are excellent corrosion inhibitors,

Fur-

these acids and their soluble metal salts are protective to other metals as well.

In the practical application of the hydroxy carboxylates a selection of concentrations should be made based on the corrosivity of the water, temperature, contacting area and rate of flow of the system involved.

In general, once the film has been established, the most economical practice in using hydroxy carboxylates for corrosion prevention is to reduce the concentration used to that amount which will continuously maintain the film as shown by little or no corrosion loss of test specimens.

Certain industrial processes such as dyeing, tanning, paper manufacture, etc., require waters of varying alkalinity, pH, and ion content for best results. The beneficial action of the inhibitor will be obtained despite the variation in the water characteristics.

Throughout the specification wherever the term hydroxy carboxylates is used, it is intended to include all hydroxy carboxylic acids and their soluble salts.

By"a gluconate" we intend to include gluconic acid as well as its soluble salts.

We have thus described our invention, but we desire it understood that it is not confined to the particular materials and methods shown and described, the same being merely illustrative, and that the invention may be carried out in other ways without departing from the spirit of our invention, and, therefore, we claim broadly the right to employ all equivalent materials and methods coming within the scope of the appended claims, and by means of which, objects of our invent on are attained and new results accomplished, as it is obvious that the particular materials and methods herein shown and described are only some of the many that can be employed to attain these objects and accomplish these results.

Having described our invention, what we claim and desire to secure by Letters Patent, is as follows:

1. The method of inhibiting water-side metallic corrosion in a water system which comprises the steps of flowing the water through a metal pipe or other container, and adding to the water in the system a gluconate to form a, concentration in the water of about from .1 to P. P. M.

2. The method of inhibiting water-side ferrous corrosion in a water system which comprises the steps of flowing the water through a ferrous metal pipe or other container, and adding to the water in the system a gluconate to form concentrations in the water of from about .1 to 100 P. P. M.

3. The method of claim 2 in which the material added to the water is gluconic acid.

4. The method of claim 2 in which the material added to the water is sodium gluconate.

5. The method of removing tuberculation from the metal surfaces of water systems which comprises flowing the water through a ferrous metal pipe or other container, and adding to the water in the system a gluconate, in concentrations of from .1 to 100 P. P. M. and continuously subjecting the tuberculation products in the system to water containing the gluconate until the tuberculation products have been removed.

6. The method of inhibiting water-side ferrous metal corrosion in a water system which comprises the steps of flowing the water through a ferrous metal pipe or other container, and adding a gluconate, in concentrations of from .1 to 100 P. P. M. to the water in the system for a period 5 of time suflicient to form a protective coating on the ferrous metal that is resistant to water-side corrosion.

'7. The method of inhibiting water-side ferrous metal corrosion in a water system which com- 5 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 4 Date 2,291,085 Lehmkuhl et a1. July 28, 1942 2,311,653 Farringtcn et al. Feb. 23, 1943 2,328,551 Gunderson Sept. 7, 1943 2,334,158 Fuchs et a1 Nov. 9, 1943 2,343,569 Neeley et a1. Mar. 7, 1944 2,371,142 Barnum et a1. Mar. 13, 1945 

1. THE METHOD OF INHIBITING WATER-SIDE METALLIC CORROSION IN A WATER SYSTEM WHICH COMPRISES THE STEPS OF FLOWING THE WATER THROUGH A METAL PIPE OR OTHER CONTAINER, AND ADDING TO THE WATER IN THE SYSTEM A GLUCONATE TO FORM A CONCENTRATION IN THE WATER OF ABOUT FROM .1 TO 100 P.P.M. 